[compositorworker] Avoid deadlock issue caused by importScript

third_party/WebKit/LayoutTests/virtual/threaded/fast/compositorworker/resources/basic-plumbing-main-to-worker.js

Index: third_party/WebKit/LayoutTests/virtual/threaded/fast/compositorworker/resources/basic-plumbing-main-to-worker.js
diff --git a/third_party/WebKit/LayoutTests/virtual/threaded/fast/compositorworker/resources/basic-plumbing-main-to-worker.js b/third_party/WebKit/LayoutTests/virtual/threaded/fast/compositorworker/resources/basic-plumbing-main-to-worker.js
index e551f837ead12a789ae9eef0de8763c6b36d265e..995c75acc0498c4b47077f141e54bb0025ca57fb 100644
--- a/third_party/WebKit/LayoutTests/virtual/threaded/fast/compositorworker/resources/basic-plumbing-main-to-worker.js
+++ b/third_party/WebKit/LayoutTests/virtual/threaded/fast/compositorworker/resources/basic-plumbing-main-to-worker.js
@@ -1,5 +1,3 @@
-self.importScripts('worker-common.js');
-
 self.onmessage = function(msg) {
   if (msg.data.proxy)
     self.proxy = msg.data.proxy;
@@ -14,3 +12,14 @@ self.onmessage = function(msg) {
     postMessage(values);
   });
 }
+
+function awaitProxyInit(proxy) {
+  return new Promise((resolve, reject) => {
+    function check() {
+      if (proxy.initialized)
+        resolve(proxy);
+      requestAnimationFrame(check);

[jbroman, 2016/07/06 15:14:00]

ex-post-facto question: This looks like it will continue to
requestAnimationFrame even after it has resolved the promise (and try to resolve
it over and over again). Should this line be in an "else" clause?

[majidvp, 2016/07/06 17:45:38]

It definitely should!

+    }
+    requestAnimationFrame(check);
+  });
+}